1. Field of the Invention
This invention is directed to a fiber entry whip reduction apparatus and a method for preventing damage to fiber, such as an optical fiber, being wound onto a rotating spool caused by the whipping action of a loose end of the fiber acting on the fiber already wound on the spool.
2. Technical Background
In the optical fiber or plastic filament manufacturing industries, long lengths of fiber or filament are wound at high speeds upon machine rotated take-up spools for shipping and handling. As the fiber is wound on the spool, the fiber is laid down onto the spool in successive layers. In the optical fiber industry, fiber winding takes place at two general locations; at the draw tower where the fiber is originally drawn, and at an off-line screening station where the fiber is strength tested. At each of these locations, the fiber can be wound at high speeds, for example, over 20 meters per second, and is maintained at relatively high tension. The apparatus for winding the fiber usually contains a relatively intricate feed assembly that includes several pulleys which guide the fiber. The pulleys facilitate proper tension on the fiber as it is wound onto the spool, while the feed apparatus facilitates uniform fiber winding onto the spool.
During winding events, the fiber is susceptible to breakage due to forces applied by the winding machine. When such fiber breaks occur, the loose end of the fiber tends to whip around at high speed due to the rapid rotation rate of the take-up spool. The uncontrolled loose fiber end can impact fiber already wound onto the spool and cause significant and irreversible damage to as many as 15 to 16 layers of the fiber. In the optical fiber industry, this can result in damage of up to 1500 meters of fiber. The break event is unpredictable, and following such a break the machine must be brought to an immediate stop to prevent whipping damage to the fiber. However, because the break is unpredictable and the spool cannot be stopped instantaneously, there is inevitably a period of time during which the spool will continue to rotate and the fiber end will be drawn toward the spool where it can whip against the fiber already wound onto the spool, thus causing damage to the fiber.
In order to prevent fiber whip damage to the fiber already wound on the spool, apparatus and methods have been developed to prevent the loose end of the fiber from striking fiber already wound on the spool. U.S. Pat. No. 5,558,287, issued to Darsey et al. discloses an apparatus and method for preventing whip damage to fiber wound onto a spool. Darsey et al. disclose a spool onto which fiber is wound, positioned above a series of brushes having bristles protruding away from the spool. As the loose end of a broken fiber flails around, it is captured by the bristles and is prevented from striking fiber on the spool. However, this type of whip protection has at least one disadvantage. The spool system requires a large and open area about which the fiber can whip relatively unobstructed. Usually, fiber winding areas are not so unobstructed.
In most cases manufacturers have guards or shields mounted for safety reasons. In many winding applications, guards on the winding machines consist of a square box around the spool, or a deflector plate mounted parallel to the spool axis of rotation. The purpose of these guards is to prevent whipping fiber from harming an operator after a break. However, these types of guards actually increase the probability that the fiber tip will strike the fiber pack. Any type of angled surface on the guard permits the free end of the fiber to strike an edge thereof, causing the fiber to wrap around the edge and rebound against the spool.
In commonly assigned U.S. patent application Ser. No. 60/050,489; the entirety of which is hereby incorporated by reference, a whip shield is disclosed. The whip shield comprises a series of arcuate portions that form a non-circular shield around the spool. As the loose end of a fiber enters the spool area, centrifugal force generated by the rotating spool maintains the loose fiber end against the shield, thereby preventing whipping damage.
However, there must be an opening in the guard to allow the fiber to be wound onto the spool. Any type of entrance opening will produce an angled edge that in turn produces the above described whip action in the fiber end.